Nippon Professional Baseball’s Saitama Seibu Lions have officially agreed to post pitcher Tatsuya Imai to Major League Baseball this offseason. Imai becomes the second Lions pitcher set to head across the Pacific this winter, joining Kona Takahashi, a rare move for any NPB club to make with two players in the same offseason.
“We determined that now is the right time to post Imai,” General Manager Koji Hiroike told the media. “He’s made great contributions to our team in recent years and has desired to play in America for a long time,” he added. Seibu now faces the difficult task of replacing two key members of their rotation, who combined for more than 300 innings this season.
The 5-foot-11 right-hander instantly becomes one of the premier arms available on the free agent market, joining names like Dylan Cease and Framber Valdez. He’s coming off a career year in 2025, posting a 1.92 ERA (156 ERA+) with a 27.8% strikeout rate over 163 2/3 innings.
Tatsuya Imai’s 2025 NPB percentiles. (Graphic by Yuri Karasawa)
The 27-year-old also led all qualified NPB pitchers with a 0.89 WHIP, ranked second with a 32.2% called strike plus whiff rate, and third with a 20.7% strikeout-minus-walk rate, all good indicators of his dominance. Long known for his shaky command, with a career walk rate of 10.8%, Imai made major strides this season by cutting that figure to a solid 7.0%.
He delivered several memorable performances during the season, including eight no-hit innings on April 18 which resulted in a combined no-hitter, a historic 17-strikeout, two-hit shutout on June 17, and back-to-back shutouts on Aug. 23 and Sept. 2.
The Tochigi, Japan native averages 95 mph on his four-seam fastball, often dialing it back to 92-93 mph against the lower part of the order and reaching 98-99 mph with runners in scoring position. He will likely be asked to sustain that higher velocity more consistently in MLB, which could lead to shorter outings.
Tatsuya Imai Pitch mix. (Graphic by Yuri Karasawa)
Imai’s best offering is his slider, which features an unusually tight movement profile often described as a “reverse slider” because of its distinctive arm-side break. It produced an elite 45.7% whiff rate in 2025, including 53.2% against right-handed hitters. Fastballs and sliders made up 93% of his total pitches to righties, reflecting his confidence in that two-pitch mix.
Against left-handers, that ratio dropped to 71% as Imai incorporated more changeups and splitters into his arsenal. He also introduced a new “sinker” late in the season (actually a vulcan changeup grip), and his growing comfort with his other secondary pitches helped him manage platoon splits better in 2025 than in previous years.
Imai’s fastball has helped him thrive as a strikeout artist over the last two seasons in Nippon Professional Baseball. He has more strikeouts than any other pitcher in NPB over the last two seasons, with 365, with 9.74 strikeouts per nine innings in that span. Compared to other free agent MLB pitchers, Imai’s strikeouts per nine innings in the last two years are higher than Zac Gallen (8.76), Framber Valdez (8.70), Ranger Suárez (8.6), Shōta Imanaga (8.2) and Chris Bassitt (8.8).
Aside from a left ankle injury in 2022 that limited him to just nine starts, the Sakushin Gakuin product has shown durability on the mound, averaging 156 innings per season since 2023. Combined with his youth and upward trajectory, he’s likely to be evaluated ahead of Kodai Senga and Shota Imanaga — both of whom entered MLB for their age-30 seasons — as a strong mid-rotation candidate in MLB despite having a shorter track record of success.
Contract projections vary, but most estimates place his value between $130-150 million, which would also require his new team to pay Seibu a posting fee of nearly $25 million on top of that.
Imai is a three-time NPB ALL-Star and could be highly coveted this offseason. However, his name enters a mix of great starting pitchers available this offseason. Along with Imai, teams in need of starting pitching will also be able to target established Major League Baseball stars, including Framber Valdez, Ranger Suárez, Brandon Woodruff, Dylan Cease, and Michael King.
Aaliyan Mohammed contributed research and writing to this report.
Photo: Tatsuya Imai is the latest NPB pitcher to be posted for MLB teams to sign. (Wikimedia Commons)
